This invention relates generally to semiconductor devices, and more specifically, to wafer grinding semiconductor wafers.
As is known, the source material for manufacturing semiconductor devices is usually a relatively large wafer, for example, of silicon. A crystal ingot is sliced to a suitable thickness to obtain a number of nearly disk-shaped wafers. Both surfaces of each wafer are subjected to abrasive machining, and then etched in a suitable mixed acid solution. One surface of each wafer is then polished to obtain a nirror-like surface. Semiconductor devices are formed on the mirror-like surface of the wafer by known processing steps of printing, etching, diffusion, doping, etc.
The silicon wafers are sliced from the crystal ingot to a thickness that is greater than desirable for a finished integrated circuit product to provide a more robust wafer to stand up to the rigors of the fabrication process. Particularly, relatively thick silicon wafers are necessary during fabrication to prevent warpage and breakage of the wafer as a result of certain heating, handling and other fabrication processes. However, the thickness of the wafer after the semiconductor devices are fabricated is greater than desirable for packaging restrictions. Therefore, it is necessary, after forming the semiconductor devices to grind a backside surface of the wafer opposite the front-side surface of the wafer where the semiconductor devices are formed to reduce the wafer thickness.
Suitable grinding machines generally include a plurality of chuck tables that secure a plurality of wafers to be ground by one or more grinding wheels. All of these devices apply a constant feed rate to the grinding wheel, which results in wafer breakage and an overheating. The overheating may burn wafer tape that is formed over the active surface of the wafer to protect it during the grinding operation. Therefore, a need exists for a grinding process or machine that does not break or overheat the semiconductor wafer during grinding.